Vibration control method for artificial satellite vibration test

This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2021-0149105, filed on Nov. 2, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety.

The present disclosure relates to a vibration control method, and more particularly, to a vibration control method for an artificial satellite vibration test.

When launch vehicles carrying artificial satellites are launched into outer space, the launch vehicles are exposed to high-temperature and high-pressure environments and undergo extreme structural vibration. Such vibration may cause damage to launch vehicles and artificial satellites loaded on the launch vehicles. To address this, the effect of vibration on artificial satellites during launch may be verified in advance by conducting an artificial satellite vibration test on the ground. For example, a vibration test is performed in a horizontal launch environment by placing a payload on a slip table and vibrating the slip table using a shaker.

In general, a vibration test is performed by installing one shaker on a slip table. In this case, the vibration test is performed assuming that the slip table is a rigid body, but the slip table cannot be treated as a rigid body in a high frequency region. In addition, a plurality of responses may not be controlled using only one shaker. Furthermore, in such a vibration test system, the absolute values of responses are used as a control parameter, and thus two completely different responses may have the same absolute value.

Moreover, in a vibration test method of the related art called a multiple input/output control method, inputs (for example, accelerations) are generated using a plurality of shakers, and resultant outputs (for example, vibration responses of a payload) are feedback controlled. In this method, however, as the number of shakers increases, the number of inputs and the number of resultant outputs increase, thereby requiring a complicated determinant and inevitably making a system sensitive to error.

Those described above are technical information that the inventors had for deriving the inventive concept or acquired while deriving the inventive concept, and may not be known to the public prior to the filling of the present application.

Provided is a vibration control method for an artificial satellite vibration test, wherein errors are reduced by selectively performing single shaker control or multiple shaker control according to frequency bands.

For example, embodiments are provided to improve the stability of multiple input/output control methods of the related art in single-axial lateral random vibration tests.

Embodiments set forth herein are examples, and embodiments of the present disclosure are not limited thereto.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure.

According to an aspect of the present disclosure, there is provided a method of controlling vibration in an artificial satellite vibration test by using a controller and a plurality of shakers installed on an artificial satellite and configured to vibrate at a predetermined frequency, the method including: performing a pre-test operation in which the controller sets the artificial satellite as a system and calculates a plurality of input values using a frequency response function of the system and an inverse matrix of the frequency response function; determining, by the controller, whether errors, which are differences between target values and a plurality of output values resulting from the plurality of input values, are within a first range; and performing, by the controller depending on results of the determination, single shaker control using one of the plurality of shakers, or multiple shaker control using the plurality of shakers.

According to some embodiments, in the method, the determining of whether the errors are within the first range may include calculating errors at predetermined frequency intervals in an entire frequency band by using one of the plurality of shakers.

According to some embodiments, in the method, when the errors are within the first range, the controller may perform the single shaker control using one of the plurality of shakers.

According to some embodiments, in the method, when the errors are outside the first range, the controller may perform the multiple shaker control using the plurality of shakers.

According to some embodiments, in the method, before performing the multiple shaker control, the controller may reduce a dimension of the frequency response function by calculating errors for combinations of the plurality of output values per predetermined frequency interval and selecting one of the combinations resulting in a minimum error.

According to some embodiments, in the method, the plurality of input values may be two in number and the plurality of output values may be three or four in number, and the controller may reduce the dimension of the frequency response function by selecting three combinations of the plurality of output values per predetermined frequency interval, calculating an error for each of the combinations, and selecting one of the combinations resulting in a minimum error such that the frequency response function may have two input values and two output values.

Other aspects, features, and advantages will become apparent and more readily appreciated from the accompanying drawings, claims, and detailed description.

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

The present disclosure may have various different forms and various embodiments, and specific embodiments are described with reference to the accompanying drawings. However, the present disclosure is not limited to the specific embodiments, and it should be understood that the idea and technical scope of the embodiments cover all the modifications, equivalents, and replacements. In the descriptions of embodiments, like reference numerals denote like elements.

Hereinafter, embodiments will be described with reference to the accompanying drawings. In the drawings, like reference numerals denote like elements, and overlapping descriptions thereof will be omitted.

In the following descriptions of the embodiments, although terms such as “first” and “second” are used to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element.

The terms of a singular form may include plural forms unless otherwise mentioned.

It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or elements, but do not preclude the presence or addition of one or more other features or elements.

Sizes of elements in the drawings may be exaggerated for ease of explanation. In other words, sizes and thicknesses of elements in the drawings are arbitrarily illustrated for ease of explanation, and thus the following embodiments are not limited thereto.

In the following embodiments, the x-axis, the y-axis and the z-axis are not limited to three axes of the rectangular coordinate system, and may be interpreted in a broader sense. For example, the x-axis, the y-axis, and the z-axis may be perpendicular to one another, or may represent different directions that are not perpendicular to one another.

When a certain embodiment is implemented differently, a specific process order may be performed differently from the described order. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order.

In the following description, the technical terms are used only for explaining a specific embodiment while not limiting the present disclosure. The term “include” or “comprise” used herein specifies the presence of a property, a fixed number, a step, a process, an element, a component, and a combination thereof, but does not exclude the presence or addition of other properties, fixed numbers, steps, processes, elements, components, and combinations thereof.

In an embodiment, an input/output vibration control device(hereinafter also referred to as a “vibration control device”) for an artificial satellite may be used in equipment for testing the vibration stability of an artificial satellite to be mounted on a launch rocket. For example, the inventive concept may be used for a single-axial lateral random vibration test in which a payload such as an artificial satellite, a part of an artificial satellite, or a launch rocket engine is mounted on a slip table and is vibrated in one direction using shakers.

Referring to, according to an embodiment, the input/output vibration control devicemay include an artificial satellite, shakers, and a controller.

The type of the artificial satelliteis not limited, and may be any one of various types of artificial satellites such as communication satellites, broadcasting satellites, weather satellites, scientific satellites, navigation satellites, earth observation satellites, technology development satellites, and military satellites. The artificial satellitemay be launched in a state in which the artificial satelliteis mounted on a launch vehicle such as a rocket.

The shakersare attached to one side of the artificial satelliteand configured to vibrate the artificial satelliteat a predetermined frequency. One or more shakersmay be arranged inside and/or outside the artificial satellite. In an embodiment, the shakersmay be electronic shakers. For example, the controllermay send a control signal to the shakersby wired or wireless communication, and then the shakersmay generate vibration corresponding to the control signal. In an embodiment, the vibration control devicemay be a dual shaker system including two shakers.

In an embodiment, each of the shakersmay include a vibration generator, an amplifier, and an accelerometer. A control signal transmitted from the controllermay be amplified by the amplifier and may then be transmitted to the vibration generator. When the vibration generator vibrates the artificial satellite, the accelerometer may display an acceleration value as an output value corresponding to the vibration and may transmit the output value back to the controller.

That is, according to an embodiment, in the input/output vibration control device, an input value may be a control signal of the controller, and an output value may be vibration information (for example, acceleration).

The controlleris configured to control a vibration test, which is performed using the input/output vibration control device. For example, the controllermay transmit a control signal to a plurality of shakersto vibrate the artificial satellite. In addition, the controllermay determine the artificial satelliteas a system to be tested and may calculate a frequency response function of the system (a characteristic function of the system) and the inverse matrix of the frequency response function to obtain an input value, that is, a control signal for obtaining a target value. Then, the controllermay transmit the control signal to the shakers. In addition, the controllermay calculate an error from the target value by controlling the shakersthrough the control signal corresponding to the input value and receiving an output value. In addition, when the error is within a first range that is previously set, the controllermay performs single shaker control (single feedback control) by controlling only one of the shakers, and when the error is outside the first range, the controllermay perform multiple shaker control (multiple feedback control) by controlling a plurality of shakers. In single shaker control, the artificial satelliteis excited, that is, vibrated using only one shaker, and in multiple shaker control, the artificial satelliteis excited using a plurality of shakers. Furthermore, in multiple shaker control, two shakersmay be operated in different frequency regions. That is, one shakermay be operated only in a low frequency region, and the other shakermay be operated in the entire frequency region.

To this end, the controllermay include: a communication module for data communication with other components of the vibration control devicesuch as the artificial satelliteand the shakers, and external devices; a calculation module configured to calculate system characteristics, input values, and errors to perform feedback control; and a control module configured to generate control signals to be transmitted to the artificial satellite, the shakers, external devices, or the like. In addition, the controllermay further include a well-known component necessary for vibration control tests, such as a display module configured to visually display a vibration test state or an input module configured to receive instructions from users.

Next, a method of controlling vibration using the vibration control devicewill be described according to embodiments with reference to.

First, referring to, the shakersare connected to the artificial satelliteand the controller. The number of shakersis not limited, and may be one or more. Hereinafter, for ease of illustration, the case in which two shakersare attached to the artificial satellitewill be mainly described. In addition, each of the shakersmay have one or more response points. For example, each of the shakersmay have one response point or two response points.

Next, the controllerperforms a pre-test operation. In the pre-test operation, the controllermay perform operations such as an operation of calculating characteristics of a system (the artificial satellitein the present disclosure) to be subjected to a vibration test and an operation of determining a control signal to be generated, that is, an input value to be generated, to determine preliminary conditions for controlling the shakers.

In an embodiment, the controllermay acquire characteristics of the system in the pre-test operation. For example, the controllermay acquire a characteristic equation representing response characteristics of the system to obtain a characteristic function of the system.

For example, characteristics of the system in a vibration test may be calculated as follows. First, when it is assumed that the system is a linear system, the system may be represented by an equation: output value Y=system H*input value X. The equation may be expressed as the following multiple input/output form in which the scale of output values are linear with input values.X=HX

Here, Xrefers to a linear spectrum of input values, Xrefers to a linear spectrum of output values, and H refers to a system characteristic matrix, that is, a frequency response matrix. For example, H may refer to a frequency response function expressing responses with respect to a driving signal of the shakers. For example, the controllermay calculate H by defining a spectrum in a frequency domain by using a Fourier transform as shown below.

Here, an input value is a driving signal (vibration signal) provided to the amplifiers of the shakers. In addition, h refers to a driving signal of the shakers. In addition, the sizes of X, X, and H are N*1, M*1, and M*N, respectively.

In an embodiment, the number of input values (driving signals) and the number of output values (responses) in the vibration control devicemay be equal to each other or different from each other. For example, the number of output values may be equal to or greater than the number of input values.

For example, when the number of input values is 2 and the number of output values is 2, X, H, and Xmay be expressed as follows.

In addition, X=HXmay be expressed as a power form in a linear space as follows.′

Here, Sand Srefer to spectral density matrices respectively indicating input values (for example, voltages) and output values (for example, accelerations). In addition, H refers to a transmissibility response function (TRF), and H′ refers to the conjugate transpose of H. In addition, T refers to target values.